Digital communication systems can be very sensitive to synchronization error. For instance, phase error can cripple a Quadrature Amplitude Modulation (QAM) system if not controlled to an acceptable level. With non-coherent FSK receivers, it is necessary to acquire and maintain an acceptable level of frequency accuracy in order to properly receive a signal. Synchronization may occur in two phases including the acquisition phase and the tracking phase. Even after a receiver acquires a signal, a transmitter may drift off frequency during a message due to such factors as heating of its local oscillator reference. In this case, the receiver is forced to track the transmitter's frequency as the message progresses.
Generally, at least one third of the software for digital communication receivers is devoted to synchronization for both acquisition and tracking of a signal. It is necessary to synchronize a received signal with a transmitted signal with respect to both time and frequency. Performance errors may result from both time and frequency synchronization errors.
Accordingly, a system is needed for achieving time and frequency synchronization between a receiver and a transmitter in an efficient manner.
Such a system may be applicable to any radio incorporating iDen talk-around for the Industrial, Scientific and Medical (ISM) band. The ISM band includes several bands in the radio frequency spectrum. These bands are unlicensed and can be used for a variety of applications. Products incorporating such technology may include two-way radios, cellular phones, and modems.